Impedance spectroscopy for emerging photovoltaics
Elizabeth von Hauff a
a Vrije University (VU) Amsterdam, De Boelelaan 1081, Amsterdam, Netherlands
Proceedings of International Conference on Impedance Spectroscopy and Related Techniques in Metal Halide Perovskites (PERIMPED)
Online, Spain, 2020 October 6th - 7th
Organizers: Juan Bisquert, Bruno Ehrler and Eline Hutter
Invited Speaker, Elizabeth von Hauff, presentation 011
Publication date: 25th September 2020

Impedance spectroscopy has been widely applied over the last decades to study electrochemical systems and solid-state devices. In the field of photovoltaics, impedance spectroscopy enables the possibility to perform in-situ characterisation under relevant operating conditions, and as function of illumination conditions, applied voltage, and ageing. It can, therefore, offer valuable insights into key loss mechanisms related to material properties and device design. However, performing impedance spectroscopy on emerging photovoltaics presents many challenges due to the ubiquitous use of multiple thin films with different physical and chemical properties, and their corresponding interfaces. As a result, the individual signatures in the impedance spectra are often difficult to interpret. In this talk, I willl discuss practical guidelines for performing impedance measurements and analysing impedance spectra. I will begin by reviewing the mathematical basics, and then discuss different strategies for choosing measurement conditions and performing data analysis. The first step is to ensure data integrity, and this depends on the measurement conditions as well as the sample itself. Impedance measurements are time-consuming, and a major source of artefacts in impedance spectra is due to sample instability. Further, knowledge of the relevant timescales of physical processes in the device, such as transport, trapping, recombination, and electron transfer at material interfaces, is a prerequisite for data analysis. I will review case studies for equivalent circuit modelling, analysis of the capacitance-frequency spectra, and performing carrier mobility measurements. 

 

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